Anti-glare film, method for manufacturing the same, and display device using the same

ABSTRACT

An anti-glare film has a plurality of diffuser elements, and has specified optical properties. The ratio of I(α+1)/I(α) is more than 0.1 to 0.6, where I(α) is an intensity of a light reflected toward an arbitrary angle α of 10° or less from a specular reflection direction of an incident light upon the surface at an angle of 5° to 30° from the surface normal, and I(α+1) is an intensity of a reflected light deviated from the arbitrary angle α by 1° in a wide-angle direction. The gain of a light reflected in the direction at 20° or more from the specular reflection direction of the incident light is 0.02 or less, in which the gain is obtained by normalizing a reflected light intensity using a specular reflection intensity of a standard diffuse plate as 1. The diffuser elements have an average space therebetween of 50 to 300 micrometers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent ApplicationNo. 2007-033855 filed in the Japanese Patent Office on Feb. 14, 2007 andJapanese Patent Application No. 2007-341220 filed in the Japanese PatentOffice on Dec. 28, 2007, the entire contents of which are incorporatedherein by reference.

BACKGROUND

The present application relates to an anti-glare film, a method formanufacturing the same, and a display device using the same.Specifically, the present application relates to an anti-glare film usedfor the surface of a displays device, such as a liquid crystal display,a plasma display, an electroluminescence display, or a cathode ray tube(CRT) display, a method for manufacturing the same, and a display deviceusing the same.

In display devices, such as a liquid crystal display, a plasma display,and a CRT display, when ambient light from fluorescent lighting or thelike is reflected in the surface of a displays device, the visibilitybecomes markedly poor. Therefore, there has been employed a method inwhich an optical multilayer film or a low refractive-index film isformed on the surface of a display device to reduce the reflectance ofthe surface or a method in which an anti-glare film having a finelyuneven surface is formed on the surface of a display device to causediffuse reflection of ambient light so that the reflected images areblurred.

However, the use of an optical multilayer film increases the productioncost, and does not achieve satisfactory anti-glare properties. When theincrease of the production cost is suppressed by using a lowrefractive-index film, the resultant surface has a relatively highreflectance, and hence a problem of annoying reflection in the surfacearises. On the other hand, in the method in which a mixture of silicafiller, organic filler or the like is incorporated to form a surfacehaving fine irregularities and a reflection in the surface of a displayis blurred utilizing diffuse reflection, anti-glare properties can beobtained; however, the appearance of white muddiness is strong, andespecially when ambient light is strong, the contrast is reduced, sothat the visibility becomes poor.

In recent years, a surface treatment which suppresses the appearance ofwhite muddiness and increases the contrast while suppressing appearanceof white muddiness is desired, and some methods for the treatment havebeen developed. For example, in the Japanese Unexamined PatentApplication Publication No. 2002-365410 (hereinafter referred to as“Patent Document 1”), a method for obtaining an anti-glare film unlikelyto be whitish while preventing reflection in the surface is disclosedwherein, the ratio of an intensity of a reflected light deviated at 20°with respect to the specular reflection direction to a specularreflection intensity of an incident light upon the direction at −10°with respect the normal to the surface of the anti-glare film is 0.2 orless and the half band width of a peak of the reflected light intensityis 7° or more.

In the Japanese Unexamined Patent Application Publication No. 2004-61853(hereinafter referred to as “Patent Document 2”) discloses an anti-glarefilm in which the specular reflectance of the incident light collimatedat an angle of 5° with the normal to the surface of the anti-glare filmis substantially equal to the reflectance toward the specular reflectiondirection of the incident light at an angle deviated by 0.2° from thespecular reflection. In addition, the Patent Document 2 also discloses amethod for obtaining an anti-glare film having a value of 1/1,000 orless in which the value is obtained by normalizing the reflected lightintensity toward the normal direction with respect to the incident lightupon the anti-glare film at 20° or more using a standard diffuser platein the same measurement (hereinafter, the reflected light intensitynormalized using an intensity of the reflected light from a standarddiffuser plate is referred to as “gain”).

The Japanese Unexamined Patent Application Publications No. 2006-53371and No. 2004-240411 (hereinafter referred to as “Patent Document 3” and“Patent Document 4” respectively) have descriptions of a method forobtaining an anti-glare film in which, the regular reflectance is 1% orless with respect to the incident light upon the anti-glare film at anangle of incidence of 5° to 30°, and the ratio of the reflectance toward30° or more with respect to the specular reflection direction to thespecular reflectance is 0.001 or less.

However, there is a trade-off between anti-glare properties andsuppression of the appearance of white muddiness, and it is difficult todesign an anti-glare film having both the properties, and the solutionhas been not good enough. For example, it has been found that a knownanti-glare film having irregularities surface formed using silica fillersatisfies the diffuse reflection characteristics specified in the patentdocument 1 and the anti-glare film exhibits a strong appearance of whitemuddiness although the intensity ratio is 0.1 or less, and theanti-glare film can achieve anti-glare properties while the half bandwidth is 7° or less.

The diffuse reflection characteristics described in the patent document2, in which the specular reflectance is substantially equal to thereflectance toward the specular direction of the incident light deviatedfrom an angle by 0.2° to the specular reflection, are satisfied by, afilm having a surface state close to the mirror reflection, andtherefore it is difficult to obtain anti-glare properties merely by thetechnique described in the Patent Document 2. On the other hand, fromthe studies made by the present inventors, it has been found that, evenwhen the gain to the normal direction is about 1/100, the appearance ofwhite muddiness of the film can be satisfactorily lowered although it isdifficult to actually prepare an anti-glare film having characteristicssuch that the gain to the normal direction is 1/1,000 or less.

Regarding the diffuse reflection characteristics specified in the PatentDocuments 3 and 4, it has been found that there are cases where ananti-glare film achieves a regular reflectance of 1% or less even thoughthe anti-glare film has a relatively even surface and a largereflection. In addition, it has been found that an anti-glare filmsubjected to a low-reflection treatment, for example, a low refractiveindex layer formed on the surface, satisfies such diffuse reflectioncharacteristics, but the anti-glare properties are not good enough.

Further, as described above, an anti-glare film having fineirregularities in the surface provides anti-glare properties, but it hasa problem in that the film has a rough surface appearance on visualperception. When an anti-glare film having a large rough surfaceappearance is used in a display device, the viewability of an imagebecomes lowered.

SUMMARY

Accordingly, it is desirable to provide an anti-glare film which isadvantageous not only in that it has suppresses the appearance of whitemuddiness while achieving anti-glare properties, but also in that it hasreduced rough surface appearance, a method for manufacturing the same,and a display device using the same.

In accordance with a first embodiment, there is provided an anti-glarefilm having a plurality of diffuser elements formed on a surface of theanti-glare film, and wherein the anti-glare film has the followingoptical properties of: (1) an I(α+1)/I(α) ratio of more than 0.1 to 0.6,wherein I(α) is an intensity of a reflected light reflected toward anarbitrary angle α of 10° or less from a specular reflection direction ofan incident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction orthe surface, and I(α+1) is an intensity of a reflected light deviatedfrom the arbitrary angle α by 1° in a wide-angle direction (arbitraryangle α plus 1°), and (2) a gain of 0.02 or less of a light reflected inthe direction at 20° or more from the specular reflection direction ofthe incident light, wherein the gain is obtained by normalizing areflected light intensity using a specular reflection intensity of astandard diffuse plate as 1. The diffuser elements have an average spacetherebetween of 50 to 300 μm.

In accordance with a second embodiment, there is provided an anti-glarefilm having a plurality of diffuser elements on the surface thereof,wherein the anti-glare film has the following optical properties of: (1)a full width of angle of 6.0° to 28.0° at the 1/100 reflected lightintensity to a peak of a reflected light intensity, with respect to anincident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface; and (2) a gain of 0.02 or less of light reflected in thedirection at 20° or more from a specular reflection direction of theincident light, wherein the gain is obtained by normalizing a reflectedlight intensity using a specular reflection intensity of a standarddiffuse plate as 1. The diffuser elements have an average spacetherebetween of 50 to 300 μm.

In accordance with a third embodiment, there is provided an anti-glarefilm having a plurality of diffuser elements on the surface thereof, andwherein the anti-glare film has the following optical properties of: (1)a full width of angle of 10.0° to 45.0° at the 1/1,000 reflected lightintensity to a peak or a reflected light intensity, with respect to anincident light upon the surface having the plurality or diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface, and (2) a gain of 0.02 or less of a light reflected in thedirection at 20° or more from a specular reflection direction of theincident light, wherein the gain is obtained by normalizing a reflectedlight intensity using a specular reflection intensity of a standarddiffuse plate as 1. The diffuser elements have an average spacetherebetween of 50 to 300 μm.

In accordance with a fourth embodiment, there is provided a method formanufacturing an anti-glare includes the step of forming lineirregularities in a surface of the anti-glare film by shape transfermethod, sandblasting method, laser beam machining method, wet etchingmethod, or Benard Cells forming method, to thereby form a plurality ofdiffuser elements on the surface. The anti-glare film has the followingoptical properties of: (1) an I(α+1)/I(α) ratio of more than 0.1 to 0.6,wherein I(α) is an intensity of a reflected light reflected toward anarbitrary angle α of 10° or less from a specular reflection direction ofan incident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface, and I(α+1) is an intensity of a reflected light deviatedfrom the arbitrary angle α by 1° in a wide-angle direction (arbitraryangle α plus 1°), and (2) a gain of 0.02 or less of a light reflected inthe direction at 20° or more from the specular reflection direction ofthe incident light, wherein the gain being obtained by normalizing areflected light intensity using a specular reflection intensity of astandard diffuse plate as 1, and wherein the diffuser elements have anaverage space therebetween of 50 to 300 μm.

In accordance with a fifth embodiment, there is provided a method formanufacturing an anti-glare film includes the step of forming fineirregularities in a surface of the anti-glare film by shape transfermethod, sandblasting method, laser beam machining method, wet etchingmethod, or Benard Cells forming method, to thereby form a plurality ofdiffuser elements on the surface. The anti-glare film has the followingoptical properties of: (1) a full Width of angle of 6.0° to 28.0° at the1/100 reflected light intensity tot a peak of a reflected lightintensity, with respect to an incident light upon the surface having theplurality of diffuser elements thereon at an angle of 5° to 30° from thenormal direction of the surface; and (2) a gain of 0.02 or less of alight reflected in the direction at 20° or more from a specularreflection direction of the incident light, wherein the gain is obtainedby normalizing a reflected light intensity using a specular reflectionintensity of a standard diffuse plate as 1, and wherein the diffuserelements have an average space therebetween of 50 to 300 μm.

In accordance with a sixth embodiment, there is provided a method formanufacturing an anti-glare film includes the step of forming fineirregularities in a surface of the anti-glare film by shape transfermethod, sandblasting method, laser beam machining method, wet etchingmethod, or Benard Cells forming method, to thereby form a plurality ofdiffuser elements on the surface. The anti-glare film has the followingoptical properties of: (1) a full width of angle of 10.0° to 45.0° atthe 1/1,000 reflected light intensity to a peak of a reflected lightintensity, with respect to an incident light upon the surface having theplurality of diffuser elements thereon at an angle of 5° to 30° from thenormal direction of the surface, and (2) a gain of 0.02 or less of alight reflected in the direction at 20° or more from a specularreflection direction of the incident light, wherein the gain is obtainedby normalizing a reflected light intensity using a specular reflectionintensity of a standard diffuse plate as 1, and wherein the diffuserelements have an average space therebetween of 50 to 300 μm.

In accordance with a seventh embodiment, there is provided a displaydevice which includes: a display portion for displaying an image, and ananti-glare film formed on a display side of the display portion. Theanti-glare film has a plurality of diffuser elements on a surface of theanti-glare film, and having the following optical properties of: (1) anI(α+1)/1(α) ratio of more than 0.1 to 0.6, wherein I(α) is an intensityof a reflected light reflected toward an arbitrary angle α of 10° orless from a specular reflection direction of an incident light upon thesurface having the plurality of diffuser elements thereon at an angle of5° to 30° from the normal direction of the surface, and I(α+1) is anintensity of a reflected light deviated from the arbitrary angle α by10° in a wide-angle-direction (arbitrary angle α plus 1°), and (2) again or 0.02 or less of a light reflected in the direction at 20° ormore from the specular reflection direction of the incident light,wherein the gain is obtained by normalizing a reflected light intensityusing a specular reflection intensity of a standard diffuse plate as 1.The diffuser elements have an average space therebetween of 50 to 300μm.

In accordance with an eighth embodiment, there is provided a displaydevice which includes a display portion for displaying an image and ananti-glare film formed on a displays side of the display portion. Theanti-glare film has a plurality of diffuser elements on a surface of theanti-glare film, and having the following optical properties of: (1) afull width of angle of 6.0° to 28.0° at the 1/100 reflected lightintensity to a peak of a reflected light intensity, with respect to anincident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface; and (2) a gain of 0.02 or less of a light reflected in thedirection at 20° or more from a specular reflection direction of theincident light, wherein the gain is obtained by normalizing a reflectedlight intensity using a specular reflection intensity of a standarddiffuse plate as 1, and wherein the diffuser elements have an averagespace therebetween of 50 to 300 μm.

In accordance with a ninth embodiment, there is provided a displaydevice which includes a display portion for displaying an image; and ananti-glare film formed on a display side of the display portion, whereinthe anti-glare film having a plurality of diffuser elements on a surfaceof the anti-glare film, and having the following optical properties of:(1) a full width of angle of 10.0° to 45.0° at the 1/1,000 reflectedlight intensity to a peak of a reflected light intensity, with respectto an incident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface, and (2) a gain of 0.02 or less of a light reflected in thedirection at 20° or more from a specular reflection direction of theincident light, wherein the gain is obtained by normalizing a reflectedlight intensity using a specular reflection intensity of a standarddiffuse plate as 1, and wherein the diffuser elements have an averagespace therebetween of 50 to 300 μm.

In each of the first, fourth, and seventh embodiment, an anti-glare filmhaving a specific ratio of the intensity of the reflected light towardan arbitrary angle of 10° or less to the intensity of the reflectedlight deviated from the arbitrary angle by 1° in a wide-angle direction(arbitrary angle α plus 1°) can achieve anti-glare properties.Specifically, with respect to a speluclar reflection direction of anincident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° relative to the normal to thesurface, an I(α+1)/I(α) ratio is more than 0.1 to 0.6, wherein I(α) isan intensity of the reflected light reflected toward an arbitrary angleα of 10° or less from the specular redlection direction, and I(α+1) isan intensity of a reflected light deviated from the arbitrary angle α 1°in a wide-angle direction (arbitrary angle α plus 1°), when theI(α+1)/I(α) ratio for the reflected light intensity is more than 0.1,anti-glare properties can be obtained, and when the I(α+1)/I(α) ratio is0.6 or less, the appearance of white muddiness can be suppressed.

In each of the second, fifth, and eighth embodiments, an anti-glare filmhaving a specific full width of angle at the 1/100 reflected lightintensity to a peak of a reflected light intensity can achieveanti-glare properties. Specifically, with respect to an incident lightupon the surface having the plurality of diffuser elements thereon at anangle of 5° to 30° relative to the normal direction of the surface, thefull width of angle at the 1/1,000 reflected light intensity withrespect to the peak of the reflected light intensity is 6.0° to 28.0°.When the full width of angle at the 1/100 reflected light intensity withrespect to the peak of reflected light intensity is 6.0° or more,anti-glare properties can be obtained, and when the full width of angleis 28.0° or less, the appearance of white muddiness can be suppressed.

In each of the third, sixth, and ninth embodiments, an anti-glare filmhaving a specific full width of angle at the 1/1,000 reflected lightintensity to a peak of a reflected light intensity can achieveanti-glare properties. Specifically, with respect to an incident lightupon the surface having the plurality of diffuser elements thereon at anangle of 5° to 30° relative to the normal direction of the surface, thefull width of angle at the 1/1,000 reflected light intensity to the peakof the reflected light intensity is 10.0° to 45.0°. When the full widthof angle at the 1/1,000 reflected light intensity to the peak ofreflected light intensity is 10.0° or more, anti-glare properties can beobtained, and when the full width of angle is 45.0° or less, theappearance of white muddiness can be suppressed.

In an embodiment, when the anti-glare film has a specific gain of thelight reflected in the direction at 20° or more from the specularreflection direction, the appearance of white muddiness can besuppressed. Specifically the gain of the light reflected in thedirection at 20° or more from the specular reflection direction is 0.02or less.

When the anti-glare film has a specific average space between thediffuser elements, the rough surface appearance can be reduced accordingto an embodiment. Specifically, the amperage space between the diffuserelements is 50 to 300 μm.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an enlarged cross-sectional view showing an example of theconfiguration of an anti-glare film according to a first embodiment.

FIGS. 2A to 2E are cross-sectional views showing an example of processesfor manufacturing an anti-glare film according to a first embodiment.

FIG. 3 is an enlarged cross-sectional view showing the configuration ofan anti-glare film according to a second embodiment.

FIG. 4 is a view diagrammatically showing an example of conditions formeasurement of diffuse reflection characteristics to an incident lightupon a surface at an angle of 5° to 30° with respect to the normaldirection of an anti-glare film according to a second embodiment.

FIG. 5 is a graph showing an example of the diffuse reflectioncharacteristics of an anti-glare film according to a second embodiment.

FIG. 6 is an enlarged cross-sectional view showing an example of theconfiguration of an anti-glare film according to a third embodiment.

FIGS. 7A to 7E are cross-sectional views showing an example of theprocess for manufacturing an anti-glare film according to a thirdembodiment.

FIG. 8 is a view showing an example of the configuration of a liquidcrystal display device using an anti-glare film according to a thirdembodiment.

FIG. 9 is a graph showing the diffuse reflection characteristics inExamples 1 and 2 and Comparative Example 2.

FIG. 10 is a graph showing the diffuse reflection characteristics inExamples 3 and 6 and Comparative Example 4.

FIG. 11 is a graph for explaining the correlation between degree ofwhite muddiness as measured using a black glass sheet and degree ofwhite muddiness as measured using a black acrylic sheet.

DETAILED DESCRIPTION

The present application will be described below in greater detail withreference to the figures according to an embodiment.

(1) First Embodiment

(1-1) Configuration of Anti-Glare Film

FIG. 1 is an enlarged cross-sectional view showing an example of theconfiguration of an anti-glare film according to a first embodiment. Aplurality of protuberances are formed on a surface 14 of an anti-glarefilm 1 as diffuser elements, so that the surface collectively has fineirregularities. The present inventors have made extensive and intensivestudies on the diffuse reflection characteristics of the anti-glare film1. As a result, it is found that the anti-glare film 1 having specificdiffuse reflection characteristics described below can achieve bothexcellent anti-glare properties and suppression of the appearance ofwhite muddiness, and have succeeded in obtaining such an anti-glarefilm.

For achieving the anti-glare properties, an absolute value of specularreflection intensity is required to be reduced, but it is more desirablethat the diffuse reflection characteristics do not sharply change. Thereis a correlation between the visual sensitivity of a human and alogarithm of the intensity of light, and therefore, when a logarithm ofthe intensity for the diffuse reflection characteristics sharplychanges, the reflection edge of a light source is visually perceived, sothat the surface exhibits no anti-glare properties. Thus, the anti-glarefilm 1 according to a first embodiment satisfies an I(α+1)/I(α) ratio ofmore than 0.1 to 0.6, wherein 1(α) is an intensity of a reflected lighttoward an arbitrary angle α of 10° or less from a specular reflectiondirection of an incident light upon a surface 14 at an angle of 5° to30° from the normal line of the surface 14, and I(α+1) is an intensityof a reflected light deviated from the angle α by 1° in a wide-angledirection. If the I(α+1)/I(α) ratio is not less than 0.1, the intensitychanges abruptly and the edge tends to become observed, whereby noanti-glare properties are perceived. If the I(α+1)/I(α) ratio is morethan 0.6, the appearance of White muddiness becomes larger although theanti-glare properties are obtained.

A full width of angle that becomes the 1/100 reflected light intensityto a peak of a reflected light intensity with respect to an lightincident from an direction of angle 5° to 30° from the normal directionof the surface 14, is 6.0° to 28.0°, so that the anti-glare propertiessimilar to the diffuse reflection characteristics specified by describedabove are achieved. If the full width of angle is not more than 6.0°,the intensity changes abruptly and the edges tends to be observed. Ifthe full width of angle is over 28.0°, the appearance of white muddinessis exhibited although the anti-glare properties are obtained.

Similarly a full width of angle that becomes the 1/1,000 reflected lightintensity to a peak of a reflected light intensity, with respect to anlight incident from an direction of angle 5° to 30° with respect to thenormal direction of the surface 14, is 10.0° to 45.0°, so that theanti-glare properties similar to the diffuse reflection characteristicsspecified by described above are achieved. If the full width of angle isnot more than 10.0°, the intensity changes abruptly and the edges tendsto be observed. If the full width of angle is over 45.0°, the appearanceof white muddiness is exhibited although the anti-glare properties areachieved.

The diffuse reflection characteristics of the anti-glare film 1 aredetermined by measuring a reflected light intensity using, e.g., agoniophotometer GP-1-3D, manufactured and sold by OPTEC Co., Ltd. In themeasurement, for removing the effect of reflection off the back surfaceto determine the diffuse reflection characteristics of the anti-glarefilm 1 per se, a black glass or black acrylic sheet is bonded through anadhesive to an opposite to the surface 14 of the anti-glare film 1.

On the other hand, regarding the appearance of white muddiness, thereflectance at an angle of 10° or more from the specular direction is ofconsequence. The reason for this is that the degree of white muddinessis lowered by reducing the light components diffusing in a wide-angledirection from the specular reflection direction. Accordingly, theanti-glare film 1 according to a first embodiment satisfies diffusereflection characteristics such that a gain of the light reflected inthe direction at 20° or more from the specular reflection direction fromthe specular reflection direction of the incident light, in which thegain is obtained by normalizing a reflected light intensity using aspecular reflection intensity of a standard diffuse plate as 1, is 0.02or less, with respect to the incident light upon the surface in thedirection at an angle of 5° to 30° from the normal to the surface 14.Preferably, the gain of light reflected toward the direction at 20° orfrom the specular reflection direction is 0.01 or less. The gain oflight reflected toward the direction at 10° or more may be 0.25 or less,more preferably 0.08 or less. Thus, the appearance of white muddiness inthe anti-glare film can be suppressed. A gain means a reflected lightintensity normalized using a standard diffuser plate, and a gain is avalue of reflected light intensity standardized using as 1 an intensityof the regular reflected light measured using a barium sulfate standarddiffuser plate in the same measurement.

The anti-glare film 1 preferable has a surface haze of 5.0% or less,more preferably 3.0% or less. If the surface haze is 5.0% or less, theanti-glare film is reduced in the appearance of white muddiness, and, ifthe surface haze is 3.0% or less, the anti-glare film is further reducedin the appearance of white muddiness. The surface haze is a valueobtained by detecting the surface scattering, and, the higher thesurface haze, the higher the appearance of white muddiness. On the otherhand, regarding the internal haze, there is no particular limitation.

An internal haze, when used herein, is determined by, for example,making a measurement with respect to the anti-glare film 1 having anadhesive having a haze of 1.0% or less attached onto the surface of theanti-glare layer 12 under the conditions for measurement described inJIS K7136 using a haze meter HM-150 (manufactured and sold by MURAKAMICOLOR RESEARCH LABORATORY). A surface haze is determined by making ameasurement with respect to the anti-glare film 1 in the same manner asin the determination of an internal haze, thereby obtaining a differencebetween the resultant value and the internal haze.

The optical properties of the anti-glare film 1 is obtained by thediffuser elements formed on the surface 14 such that the surface 14 hasfine irregularities. By reducing the size of the diffuser elements,scintillation caused due to the rough surface appearance on visualperception or glare of the screen (hereinafter, the glare of the screenis frequently referred to as “surface glare”) can be suppressed.

The rough surface appearance on visual perception means that theperceived granularity having uneven luminance is observed by reflectionsoff one diffuser element in different directions when reflecting a lightsource having a uniform light intensity off the anti-glare film 1.Accordingly, it is advantageous that the space between the diffuserelements is reduced so that the individual diffuser elements can beseparated from one another when observed at the optimum viewing distanceof an image display device using the anti-glare film 1. Specifically,the rough surface appearance can be suppressed by reducing the averagespace between the diffuser elements when the diffuser elements arespecified by volume diffusion, or reducing the average peak-valley spaceSm when the diffuser elements are specified by surface diffusion.

Accordingly, the anti-glare film 1 according to a first embodimentsatisfies characteristic such that the average space between thediffuser elements, namely, the average peak-valley space Sm of thesurface 14 is 300 μm or less, more preferably 220 μm or less. Theaverage space between the diffuser elements, namely, the averagepeak-valley space Sm of the surface 14 of the anti-glare film 1 ispreferably 2 μm or more from the viewpoint of appropriately controllingthe diffuse reflection characteristics and preventing coloration, and ispreferably 50 μm or more from the viewpoint of practical controllingproperties.

A resolution d (dpi) of a person having a visual acuity V such that theperson can distinguish white from black in respect of a subject placedat a distance D (cm) from the person is determined by the followingformula:

d=2.54×3,438×V/D

From the calculation, it is found that the resolution of a person havinga visual acuity of 1.0 at a viewing distance of 100 centimeters(cm) isabout 290 micrometers (μm). Therefore, it is considered that, when theaverage peak-valley space Sm falls within the above range, the roughsurface appearance can be suppressed.

The average peak-valley space Sm of the anti-glare film 1 is determinedas a roughness parameter from a roughness curve obtained by measuringsurface roughness in accordance with the method described in JISB0601-1994 using. e.g., SURFCORDER ET4000A, manufactured and sold byKosaka Laboratory Ltd., as an Automatic Microfigure MeasuringInstrument.

On the other hand, the surface glare is affected by the relationshipbetween the space between the diffuser elements of the anti-glare film 1and the pixel pitch, and therefore it is preferred to control the spaceaccording to the pixel pitch of the image display device used. When thespace between the diffuser elements is not smaller than the pixel pitch,the relative positional relationship is not uniform between theindividual diffuser elements, so that it is recognized as surface glare.Therefore, when the space between the diffuser elements is ⅓ or less,more preferably ¼ or less of the pixel size of the image display device,surface glare can be prevented.

The anti-glare film 1 having fine irregularities in the surface thereofin a first embodiment is composed of, for example, a resin. The resinused for the anti-glare film 1 includes at least one of an ionizingradiation-curable resin which is cured by, for example, ultravioletradiation or electron radiation, a thermosetting resin which is cured byheating, or a thermoplastic resin, from the viewpoint of facilitatingthe production. As the ionizing radiation-curable resin, an acrylateresin, such as urethane acrylate, epoxy acrylate, polyester acrylate,polyol acrylate, poly ether acrylate, or melamine acrylate, may be used.With respect to the properties of the cured resin, especially preferredis a resin which produces a cured resin having excellent permeability tolight from the viewpoint of achieving image permeability or a resinwhich produces a cured resin having high hardness from the viewpoint ofobtaining a flaw resistance, and a resin can be appropriately selected.The ionizing radiation-curable resin is not limited to an ultravioletcuring resin, and any ionizing radiation-curable resin may be used aslong as it has permeability to light, but preferred is an ionizingradiation-curable resin which does not markedly change in hue of thetransmitted light or transmitted light amount due to coloration or haze.

The photosensitive resin is obtained by incorporating aphotopolymerization initiator into an organic material which is capableof forming a resin, such as monomers, oligomers, or a polymer. Forexample, an urethane acrylate resin is obtained by reacting isocyanatemonomers or a prepolymer with polyester polyol and reacting acrylate ormethacrylate monomers having a hydroxyl group with the resultantproduct.

As the photopolymerization initiator, for example, a benzophenonederivative, an acetophenone derivative, an anthraquinone derivative, andthe like can be used individually or in combination. In thephotosensitive resin, a component for facilitating the film formation,such as an acrylic resin, may be appropriately selected andincorporated.

In the photosensitive resin, a light stabilizer, an ultraviolet lightabsorber, an antistatic agent, a flame retardant, an antioxidant, or thelike may be added in an appropriate amount if desired. Silica fineparticles or the like may be added as a viscosity modifier.

(1-2) Method for Manufacturing an Anti-Glare Film

A method for manufacturing the anti-glare film 1 according to a firstembodiment is described with reference to FIGS. 2A to 2E.

(Process for Preparing a Mother Die)

A base material to be processed is first prepared. Examples of forms ofthe base material include a substrate form, a sheet form, a film form,and a block form. Examples of materials for the base material includeplastics, metals, and glass. Then, the base material is processed usinga mask imaging method using, e.g., a KrF excimer laser, a pressingmethod, a method using a stamper for molding, a cutting method, asandblasting method, a wet etching method, or the like to pattern in thesurface of the base material fine irregularities corresponding to thesurface 14 of the anti-glare film 1, thereby obtaining a mother die 21having an inverse fine irregularities of the shape in the surface 14 asshown in FIG. 2A. The surface of the mother die 21 has fineirregularities such that the anti-glare film 1 can achieve diffusereflection characteristics as described above, and has an averagepeak-valley space Sm of 300 μm or less, preferably 220 μm or less.

(Process for Preparing a Duplicate Master)

Next, a conducting film is formed on the fine irregularities of theabove-obtained mother die 21 by, for example, an electroless platingmethod. The conducting film is a metal film composed of a metal, such asnickel. Then, the mother die 21 having a conducting film formed thereonis set in an electroforming apparatus, and a metal plating layer, suchas a nickel plating layer, is formed on the conducting film by, forexample, an electroplating method. The metal plating layer is thenreleased from the mother die 21, obtaining a duplicate master 22 havingan inverse fine irregularities of the shape in the mother die 21 asshown in FIG. 2B.

Then, the above-obtained duplicate master 22 is subjected to surfacetreatment, and then a metal plating layer, such as a nickel platinglayer, is formed on the fine irregularities of the resultant duplicatemaster by, for example, an electroplating method. The metal platinglater is then released from the duplicate master 22, thereby obtaining aduplicate master 23 having the same fine irregularities as that of themother die 21 as shown in FIG. 2C.

When the mother die is composed of an organic substance or the like,which is likely to be damaged, a child mold and a grandchild mold areprepared from the mother die as described above, and a grandchild moldis prepared in a great amount using the child mold even when the motherdie is damaged upon releasing the mother die. On the other hand, whenthe mother die is unlikely to be damaged and a child mold may berepeatedly prepared from the mother die, the mother die is processed sothat it has the same shape as that of the anti-glare layer and theresultant reverse child mold may be used as a transfer mold.

(Process for Preparing an Anti-Glare Film)

Next, a photosensitive resin such as an ultraviolet curing resin ispoured into the fine irregularities of the above-obtained duplicatemaster 23, as shown in FIG. 2D, to render the thickness of thephotosensitive resin uniform. The fine irregularities of the surface 14is obtained by shape transfer, and hence it is not necessary to add fineparticles to the photosensitive resin, but fine particles may be addedto the photosensitive resin for finely controlling the haze or surfaceshape.

And then, by a photo-irradiation such as ultraviolet irradiation fromthe side of the poured photosensitive resin, the resin is cured. Then,as shown in FIG. 2E, the cured photosensitive resin is released from theduplicate master 23. Thus, the anti-glare film having fineirregularities which is a moderate waviness in the surface 14 isobtained.

The anti-glare film 1 prepared by the above processes has specificdiffuse reflection characteristics as described above and hencesuppresses the appearance of white muddiness while providing anti-glareproperties. Further, the anti-glare film has a specific space betweenthe diffuser elements formed in the surface 14, and hence reduces roughsurface appearance. Accordingly by using the anti-glare film 1 in adisplay device, such as a liquid crystal display, a plasma display, anelectroluminescence display, or a CRT display, display achieving bothexcellent anti-glare properties and excellent contrast can be provided,thereby improving the visibility.

(2) Second Embodiment

(2-1) Construction of Anti-Glare Film

FIG. 3 is an enlarged cross-sectional view showing an example of theconstruction of an anti-glare film according to a second embodiment. Ananti-glare film 1 includes a substrate 11, and an anti-glare layer 12having fine particles 13 formed on the substrate 11. The fine particles13 form a plurality of protuberances as diffuser elements in the surfaceof the anti-glare layer 12. Consequently, the surface of the anti-glarelayer 12 collectively has fine irregularities. The present inventorshave made extensive and intensive studies on the diffuse reflectioncharacteristics of the anti-glare film 1. As a result, it is found thatthe anti-glare film 1 having specific diffuse reflection characteristicsdescribed below can achieve both excellent anti-glare properties andsuppression of the appearance of white muddiness, and have succeeded inobtaining such an anti-glare film.

For achieving the anti-glare properties, an absolute value of intensityof the regular reflected light is required to be reduced, but it is moredesirable that the diffuse reflection characteristics do not sharplychange. There is a correlation between the visibility of a human and alogarithm of the intensity of light, and therefore, when a logarithm ofthe intensity for the diffuse reflection characteristics sharplychanges, the edge of a reflection of a light source in the surface isvisually recognized, so that the surface exhibits no anti-glareproperties. Therefore, the anti-glare film 1 according to an secondembodiment of present invention satisfies diffuse reflectioncharacteristics such that, with respect to the incident light upon thesurface of the anti-glare layer 12 in the direction 3 at an angle of 5°to 30° from the normal 2 to the surface as shown in FIG. 4, anI(α+1)/I(α) ratio is more than 0.1 wherein I(α) is an intensity of thereflected light in the direction 5 at an arbitrary angle α of 10° orless from the specular direction 4, and I(α+1) is an intensity of thereflected light in the direction 6 at the angle α by 1° in a wide-angledirection. In this case, a change or the logarithm of the intensity ofthe reflected light can be −1 or smaller, and hence the edge of areflection is no longer distinct, thus obtaining anti-glare properties.On the other hand, when the I(α+1)/I(α) ratio for the reflected lightintensity is increased, the anti-glare properties can be obtained, butthe appearance of white muddiness becomes stronger. Therefore, theI(α+1)/I(α) ratio for the reflected light intensity is 0.6 or less.

FIG. 5 is a graph showing an example of the relationship between anangle (α) and a reflected light intensity I(α) when the speculardirection is 0° with respect to the incident light upon the surface ofthe anti-glare layer 12. Arrows in the figure indicate the full width ofangle at the 1/100 reflected light intensity with respect to the peak ofreflected light intensity. It has been found that, with respect to theincident light upon the surface of the anti-glare layer 12 in thedirection 3 at an angle of 5 to 30° from the normal 2 of the surface,when the full width of angle at the 1/100 reflected light intensity withrespect to the peak of reflected light intensity is 6.0° to 28.0°,anti-glare properties similar to the above specific diffuse reflectioncharacteristics can be achieved. When this full width of angle is lessthan 6.0°, a change of the intensity is such sharp that the edge or areflection is likely to be observed. On the other hand, when the fullwidth of angle is more than 28.0°, anti-glare properties are obtained,but the appearance of white muddiness is exhibited.

Similarly, it has been found that, regarding the incident light upon thesurface of the anti-glare layer 12 in the direction 3 at an angle of 5°to 30° from the normal 2 of the surface, when the full width of angle atthe 1/1,000 reflected light intensity with respect to the peak ofreflected light intensity is 10.0° to 45.0°, anti-glare propertiessimilar to the above specific diffuse reflection characteristics can beobtained. The full width of angle at the 1/10 reflected light intensitywith respect to the peak can be similarly specified, but the diffusereflection characteristics of a surface having gloss such that areflection is seen and those of a surface having appropriate anti-glareproperties are similar to each other at an angle at the about 1/10intensity, and it has been found that the anti-glare properties are notobtained merely by specifying the diffuse reflection characteristics.

The diffuse reflection characteristics of the anti-glare film 1 aredetermined by measuring a reflected light intensity using, e.g., agoniophotometer GP-1-3D, manufactured and sold by OPTEC Co., Ltd. In themeasurement, for removing the effect of reflection off the back surfaceto determine the diffuse reflection characteristics of the anti-glarefilm 1 per se, a black glass or black acrylic sheet is bonded through anadhesive to the surface of the anti-glare film 1 on which the anti-glarelayer 12 is not formed.

On the other hand, regarding the appearance of white muddiness, thereflectance at an angle of 10° or more from the specular reflectiondirection is of consequence. The reason for this is that the degree ofwhite muddiness degree can be lowered by reducing the light componentsdiffused at angles larger than the angle of the specular reflectiondirection from the normal of the surface. Accordingly, in the anti-glarefilm 1 according to an first embodiment, with respect to the incidentlight upon the surface of the anti-glare layer 12 in the direction 3 atin angle of 5° to 30° from the normal 2 of the surface, diffusereflection characteristics such that a gain of the light reflected inthe direction at 20° or more from the specular reflection direction is0.02 or less, more preferably 0.01 or less, as normalized using anintensity of the specular reflected light from a standard diffuser plateas 1, are satisfied, and it is advantageous that a gain of the lightreflected in the direction at 10° or more from the specular reflectiondirection is 0.25 or less, more preferably 0.08 or less. In this case,the appearance of white muddiness in the anti-glare film can besuppressed. A “gain” used herein means a reflected light intensitynormalized using a standard diffuser plate, and, in an embodiment, again is a value of reflected light intensity normalized using as 1 anintensity of the regular reflected light measured using a barium sulfatestandard diffuser plate in the same measurement.

The anti-glare film 1 preferably has a surface haze of 5.0% or less,more preferably 3.0% or less. When the surface haze is 5.0% or less, theanti-glare film is reduced in the appearance of white muddiness, and,when the surface haze is 3.0% or less, the anti-glare film is furtherreduced in the appearance of white muddiness. The surface haze is avalue obtained by detecting the surface scattering, and, the higher thesurface haze, the higher the appearance of white muddiness. On the otherhand, with respect to the internal haze, there is no particularlimitation, and it is determined depending on the fine particles 13contained in the anti-glare layer 12 and the like.

In an embodiment, an internal haze is determined by, for example, makinga measurement of the anti-glare film 1 having an adhesive having a hazeof 1.0% or less bonded onto the surface of the anti-glare layer 12 underthe conditions for measurement described in JIS K7136 using a haze meterHM-150 (manufactured and sold bit MURAKAMI COLOR RESEARCH LABORATORY). Asurface haze is determined by making a measurement with respect to theanti-glare film 1 in the same manner as in the determination of aninternal haze, and obtaining a difference between the resultant valueand the internal haze.

Such optical characteristics of the anti-glare film 1 are obtained bythe diffuser elements formed on the surface of the anti-glare layer 12such that the surface of the anti-glare layer 12 has fineirregularities. By reducing the size of the diffuser elements,scintillation caused due to rough surface appearance of the surface orglare of the screen (hereinafter, the glare of the screen is frequentlyreferred to as “surface glare”) can be suppressed.

The rough surface appearance of the surface means uneven luminance fromthe surface caused by reflections off one diffuser element in differentdirections when reflecting a light source having a uniform lightintensity of the anti-glare film 1. Therefore, it is advantageous thatthe space between the diffuser elements is reduced so that theindividual diffuser elements can be separated from one another wellobserved at the optimum viewing distance of an image display deviceusing the anti-glare film 1. Specifically, the rough surface appearancecan be suppressed by reducing the average space between the diffuserelements when the diffuser elements are specified by volume diffusion,or reducing the average peak-valley space Sm when the diffuser elementsare specified by surface diffusion.

Accordingly, the anti-glare film 1 according to a second embodimentsatisfies characteristic such that the average space between thediffuser elements, namely, the average peak-valley space Sm of thesurface of the anti-glare layer 12 is 300 μm or less, more preferably220 μm or less. The average space between the diffuser elements, namely,the average peak-valley space Sm of the surface of the anti-glare layer12 is preferably 2 μm or more from the viewpoint of appropriatelycontrolling the diffuse reflection characteristics and preventingcoloration, and is preferably 50 μm or more from the viewpoint ofpractical controlling properties.

A resolution d (dpi) of a person having a visual acuity V such that theperson can distinguish white from black in respect of a subject placedat a distance D (cm) from the person is determined by the followingformula:

d=2.54×3,438×V/D

From the calculation, it is found that the resolution of a person havinga visual acuity of 1.0 at a viewing distance of 100 centimeters (cm) isabout 290 micrometers (μm). Therefore, it is considered that, when theaverage peak-valley space Sm falls within the above range, the roughsurface appearance can be reduced.

The average peak-valley space Sm of the anti-glare film 1 is determinedas a roughness parameter from a roughness curve obtained by measuringsurface roughness in accordance with the method described in JISB0601-1994 using, e.g., SURFCORDER ET4000A, manufactured and sold byKosaka Laboratory Ltd., as an Automatic Microfigure MeasuringInstrument.

On the other hand, the surface glare is affected by the relationshipbetween the space between the diffuser elements of the anti-glare film 1and the pixel pitch, and therefore it is preferred to control the spaceaccording to the pixel pitch of the image display device used. When thespace between the diffuser elements is not smaller than the pixel pitch,the relative positional relationship is not uniform between theindividual diffuser elements, so that it is recognized as surface glare.Therefore, when the space between the diffuser elements is ⅓ or less,more preferably ¼ or less of the pixel size of the image display device,surface glare can be prevented.

The anti-glare layer 12 according to a second embodiment, which has fineirregularities of the surface, includes, for example, a resin includingfine particles 13. In the fine irregularities of the surface, it ispreferable that the fine particles 13 are covered with a resin, such asan ionizing radiation-curable resin. The irregularities may be amoderately sloping irregularities, and, for example, it is preferredthat a plurality of fine particles 13 are appropriately agglomerated inthe in-plane direction to form one diffuser element. Either the wholesurface of the agglomerated fine particles 13 may be covered with aresin, such as an ionizing radiation-curable resin or a thermosettingresin, or the surface of the fine particles 13 may be exposed as long asthe above-mentioned diffuse reflection characteristics are satisfied.However, when the fine particles 13 protrude from the anti-glare layer12 to form a steep slope portion, it is difficult to satisfy the abovediffuse reflection characteristics, and further the surface is likely tohave rough surface appearance. Therefore, when the surface of the lineparticles 13 is exposed, it is preferred that only part of the surfaceof the fine particles 13 positioned at, for example, a tip portion 7 ofprotuberances as the diffuser elements is an exposed portion.

The term “a plurality of fine particles 13 are appropriatelyagglomerated in the in-plane direction” as used herein means: (1) thatall the fine particles 13 are agglomerated only in the in-planedirection without being stacked on one another in the thicknesswisedirection of the anti-glare layer 12; or (2) that almost all the fineparticles 13 are agglomerated in the in-plane direction and theremaining fine particles 13 are stacked on one another in thethicknesswise direction so that the degree of white muddiness is notincreased (to more than 2.0 as measured using a black glass sheet). Allthe fine particles 13 ideally form two-dimensional agglomerates, butpart of the fine particles 13 may be separate from one another withoutforming aggregates so that the degree of white muddiness is notincreased.

As a resin used in the anti-glare layer 12, from the viewpoint offacilitating the production, an ionizing radiation-curable resin whichis curable by irradiation with, e.g., ultraviolet light or an electronbeam, or a thermosetting resin which is curable by heat is preferred,and the most preferred is a photosensitive resin which is curable byirradiation with ultraviolet light. As the photosensitive resin, anacrylate resin, such as urethane acrylate, epoxy acrylate, polyesteracrylate, polyol acrylate, polyether acrylate, or melamine acrylate, canbe used. With respect to the properties of the cured resin, especiallypreferred is a resin which can produce a cured resin having excellentpermeability to light from the viewpoint of achieving imagepermeability, or a resin which can produce a cured resin having highhardness from the viewpoint of obtaining a flaw resistance, and a resinmay be appropriately selected. The ionizing radiation-curable resin isnot limited to an ultraviolet curing resin, and any ionizingradiation-curable resin may be used as long as it has permeability tolight, but preferred is an ionizing radiation curing resin which doesnot markedly change in hue of the transmitted light or transmitted lightamount due to coloration or haze.

The photosensitive resin is obtained by incorporating aphotopolymerization initiator into an organic material which is capableof forming a resin, such as monomers, oligomers, or a polymer. Forexample, an urethane acrylate resin is obtained by reacting isocyanatemonomers or a prepolymer with polyester polyol and reacting acrylate ormethacrylate monomers having a hydroxyl group with the resultantproduct.

As the photopolymerization initiator, for example, a benzophenonederivative, an acetophenone derivative, an anthraquinone derivative, andthe like may be used individually or in combination. In thephotosensitive resin, a component for facilitating the film formation,such as an acrylic resin, may be appropriately selected andincorporated.

In the photosensitive resin, a light stabilizer, an ultraviolet lightabsorber, any antistatic agent, a flame retardant, an antioxidant, orthe like may be added in an appropriate amount if desired. Silica fineparticles or the like may be added as a viscosity modifier.

As the fine particles 13, for example, organic fine particles orinorganic fine particles are used. As organic fine particles, beads,such as acryl, styrene, acryl-styrene copolymer, melamine, orpolycarbonate beads, can be used. They may be either cross-linked oruncross-linked, and any spherical or flattened fine particles comprisedof a plastic can be used. As the fine particles 13, for example, thosehaving an average particle diameter of 5 nanometers (nm) to 15micrometers (μm) are used. When the average particle diameter of thefine particles is more than 15 μm, light reflected off the surfacedisadvantageously causes glare. On the other hand, when the averageparticle diameter is less than 5 nm, the particles dispersed uponpreparing the coating composition are disadvantageously agglomeratedagain. The average particle diameter of the fine particles 13 can bemeasured by, for example, a laser diffraction method.

The anti-glare film 1 may have, although not shown, a layer containingfiller or containing no filler formed on the anti-glare layer 12, i.e.,an anti-glare layer composed of two layers.

As the substrate 11, for example, a plastic film having transparency isused. As such a film, a known polymer film may be used. Specifically, apolymer film may be appropriately selected from films comprised of knownresins, such as triacetylcellulose, polyester, polyethyleneterephthalate (PET), polyimide (PI), polyamide, aramid, polyethylene,polyacrylate, polyether sulfone, polysulfone, diacetylcellulose,polypropylene, polyvinyl chloride, an acrylic resin, polycarbonate, anepoxy resin, an urea resin, an urethane resin, and a melamine resin. Thesubstrate is not limited to a film, and, for example, a sheet or platecomprised of a plastic having transparency can be used.

Regarding the thickness of the substrate 11, there is no particularlimitation and the thickness is appropriately selected. From theviewpoint of achieving excellent productivity, it is preferred that thethickness of the substrate is 38 to 100 μm, but the thickness is notlimited to this range.

(2-2) Method for Manufacturing an Anti-Glare Film

Next, a method for manufacturing the anti-glare film 1 according to asecond embodiment is described. A solvent is first mixed into, forexample, the above-mentioned ionizing radiation-curable resin, fineparticles 13, and optionally a light stabilizer, an ultraviolet lightabsorber, an antistatic agent, a flame retardant, an antioxidant, or thelike to prepare a coating composition having the fine particles 13dispersed therein. Regarding the solvent, there is no particularlimitation, and an organic solvent, such as t-butanol, toluene, methodethyl ketone (MEK), or isopropyl alcohol (IPA), may be used.

Then, the coating composition prepared is applied substantiallyuniformly to the above-mentioned substrate 11. Regarding the method forapplying the coating composition, there is no particular limitation, anda known coating method may be used. Examples of coating methods includea microgravure coating method, a wire bar coating method, a directgravure coating method, a die coating method, a dipping method, a spraycoating method, a reverse-roll coating method, a curtain coating method,a comma coating method, a knife coating method, and a spin coatingmethod.

Regarding the thickness of the coating composition applied, the solidscontent of the coating composition is appropriately controlled andapplied so that the dried average thickness becomes 3 to 30 μm,preferably 4 to 15 μm. When the thickness is smaller than the aboverange, it is difficult to obtain a desired hardness, and, when thethickness is larger than the above range, the resultant film is likelyto suffer marked curling.

After the coating, the coating composition applied is dried at a hightemperature to volatilize the solvent. Convection caused in the coatingcomposition during the drying forms Benard Cells, enabling the surfaceof the anti-glare layer 12 to have moderately sloping irregularitieshaving an appropriate period. In the anti-glare film 2 according to asecond embodiment, a desired surface shape is obtained not by, forexample, uniformly dispersing the individual fine particles 13 but bypermitting a plurality, of fine particles 13 to be appropriatelyagglomerated due to the convection to form one diffuser element. Thedrying temperature and drying time may be appropriately determineddepending on the boiling point of the solvent contained in the coatingcomposition. In this case, it is preferred to select the dryingtemperature and drying time so that the substrate 11 does not sufferdeformation due to heat shrinkage while considering the heat resistanceof the substrate 11. Further, it is preferred to control the conditionsfor drying and others so that appropriate convection is caused in anionizing radiation curing resin to produce a desired surface shape.

The drying step and curing step are described below in detail.

The coating composition applied to the substrate 11 is first dried at apredetermined temperature to cause convection in the coating compositionso that the fine particles 13 are appropriately agglomerated in thein-plane direction due to the convection, forming two-dimensionalaggregates. In this instance, the solvent is volatilized, and BenardCells are formed in the surface of the applied film. When the fineparticles 13 are stacked on one another in the thicknesswise directionof the applied film to form three-dimensional agglomerations, componentshaving sharp angles are disadvantageously formed in the surface of theanti-glare layer, thus increasing the appearance of white muddiness.

The term “Benard Cells” used herein means a surface structure formed dueto a convection phenomenon or convection caused in the coatingcomposition in the drying step for solvent. All of the surfacestructures formed during the process for drying the solvent are referredto as “Benard Cells” used herein, and they have arbitrary forms, and arenot limited to a tubular structure.

The degree of the agglomeration of the fine particles 13 may be selectedby appropriately controlling, for example, the surface tension of thesolvent and the surface energy of the fine particles 13.

It is preferred that the resin contained in the coating composition isalso in the liquid state after drying the coating composition. In thiscase, meniscuses can be formed between the Benard Cells, making itpossible to produce moderately sloping fine irregularities in thesurface of the applied film.

Regarding the conditions for drying, there is no particular limitation,and there may be employed either air drying or artificial drying inwhich the drying temperature or drying time is controlled. When a streamof air is sent to the surface of the coating composition during thedrying, it is preferred that a wind-wrought pattern is not caused in thesurface of the applied film. When a wind-wrought pattern is caused,desired moderately sloping fine irregularities is unlikely to be formedin the surface of the anti-glare layer, thus making it difficult toachieve both the anti-glare properties and high contrast.

Next, the dried resin on the substrate 11 is cured by, i.e., ionizingradiation or heating. Thus a waviness with a large period are formedsuch that one two-dimensional agglomeration constitutes one peak. Thatis, fine irregularities having a broad period and a moderate slope, ascompared to irregularities in a film currently manufactured, are formedin the surface of the anti-glare layer 12.

Examples of curing energy sources used for curing an ionizingradiation-curable resin to form the anti-glare layer 12 include anelectron beam, ultraviolet light, visible light, and a gamma ray, but,from the viewpoint of the productive facilities, preferred isultraviolet light. Regarding the ultraviolet light source, there is noparticular limitation, and a high-pressure mercury lamp, a metal halidelamp, or the like is appropriately selected. Regarding the amount oftotal irradiation, there may be appropriately selected an amount oftotal irradiation such that the resin used is cured and the resin andthe substrate 11 do not suffer yellowing. The atmosphere for irradiationmay be appropriately selected depending on the curing of the resin, andthe irradiation may be performed in air or in an inert atmosphere ofnitrogen gas, argon gas, or the like.

The anti-glare film 1 prepared bay the above method has specific diffusereflection characteristics as described above, and hence suppresses theappearance of white muddiness while achieving anti-glare properties.Further, the anti-glare film has a specific space between the diffuserelements formed in the surface of the anti-glare layer 12, and hence hasreduced rough surface appearance. Therefore, by using the anti-glarefilm 1 in a display device, such as a liquid crystal display, a plasmadisplay, an electroluminescence display, or a CRT display, displayachieving both excellent anti-glare properties and excellent contrastcan be realized, thus improving the visibility.

(3) Third Embodiment

(3-1) Configuration of Anti-Glare Film

As shown in FIG. 4, an anti-glare film 1 according to a third embodimentincludes an anti-glare layer 12 formed on a substrate 11, and aplurality of protuberances are formed as diffuser elements in thesurface of the anti-glare layer 12, and the surface collectively hasfine irregularities. The fine irregularities in the surface of theanti-glare layer 12 are formed by a shape transfer method using aduplicate master prepared from a mother die formed by microfabrication.The substrate 11, diffuse reflection characteristics, and average spacebetween the diffuser elements in a third embodiment are similar to thosein first and second embodiments, and therefore the descriptions of themare omitted.

The anti-glare layer 12 in a third embodiment is formed from a resinincluding an ionizing radiation-curable resin or thermoplastic resinsimilar to that in first and second embodiments. Desired irregularitiesin the surface of the anti-glare layer 12 are obtained by, using aduplicate master as described below, transfer of irregularities in themold surface. The anti-glare layer 12 does not necessarily contain fineparticles 13, but it may contain them for finely controlling the haze orsurface shape.

(3-2) Method for Manufacturing an Anti-Glare Film

A method for manufacturing the anti-glare film 1 according to a thirdembodiment is described below with reference to FIGS. 7A to 7E.

Process for Preparing a Mother Die

A base material to be processed is first prepared. Examples of forms ofthe base material include a substrate form, a sheet form, a film form,and a block form. Examples of materials for the base material includeplastics, metals and glass. Then, the base material is processed using amask imaging method using, e.g., a KrF excimer laser, a pressing method,a method using a stamper for molding, a cutting method, a sandblastingmethod, a wet etching method, or the like to pattern in the surface ofthe base material fine irregularities corresponding to the surface ofthe anti-glare layer 12, obtaining a mother die 21 having an inversefine irregularities of the shape in the anti-glare layer 12 as shown inFIG. 7A. The surface of the mother die 21 has fine irregularities suchthat the anti-glare film 1 according to a third embodiment can achievediffuse reflection characteristics similar to those in first and secondembodiments, and preferably has an average peak-valley space Sm of 300μm or less, more preferably 220 μm or less.

Process for Preparing a Duplicate Master

Next, a conducting film is formed on the fine irregularities of theabove-obtained mother die 21 by, for example, an electroless platingmethod. The conducting film is a metal film composed of a metal, such asnickel. Then, the mother die 21 having an electrically conductive filmformed thereon is set in an electroforming apparatus, and a metalplating layer, such as a nickel plating layer, is formed on theelectrically conductive film by, for example, an electroplating method.The metal plating layer is then released from the mother die 21,obtaining a duplicate master 22 having an inverse fine irregularities ofthe shape in the mother die 21 as shown in FIG. 7B.

Then, the duplicate master 22 obtained as described above is subjectedto surface treatment, and then a metal plating layer, such as a nickelplating layer, is formed on the fine irregularities of the resultantduplicate master by, for example, an electroplating method. The metalplating layer is then released from the duplicate master 22, obtaining aduplicate master 23 having the same fine irregularities as that of themother die 21 as shown in FIG. 5C.

When the mother die is composed of an organic substance or the like,which is likely to be damaged, a child mold and a grandchild mold areprepared from the mother die as described above, and a grandchild moldmay be prepared in a great amount using the child mold even when themother die is damaged upon releasing the mother die. On the other hand,when the mother die is unlikely to be damaged and a child mold may berepeatedly prepared from the mother die, the mother die is processed sothat it has the same shape as that of the anti-glare layer and theresultant reverse child mold may be used as a transfer mold.

Process for Preparing an Anti-Glare Layer

Next, a photosensitive resin, such as an ultraviolet-curable resin, ispoured onto the fine irregularities of the duplicate master 23 obtainedby the above processes. As a photosensitive resin forming the anti-glarelayer 12, for example, a resin similar to that used in a firstembodiment may be used. The fine irregularities of the anti-glare layer12 is obtained by shape transfer, and hence it is not necessary to addfine particles to the photosensitive resin, but fine particles may beadded to the photosensitive resin for finely controlling the haze orsurface shape.

Then, as shown in FIG. 7D, a substrate 11 as a support substrate is puton the duplicate master 23. Subsequently, force is applied to thesubstrate 11 by means of, e.g., a rubber roller so that the thickness ofthe photosensitive resin becomes uniform. Then, for example, thephotosensitive resin is cured by irradiating, e.g., the substrate 11with a ray of light, such as ultraviolet light. Then, as shown in FIG.5E, the cured photosensitive resin is released from the duplicate master23. Thus, an anti-glare layer 12 is formed on one principal surface ofthe substrate 11, preparing an anti-glare film 1 having the diffusereflection characteristics as described above.

FIG. 8 is a view showing an example of the configuration of a liquidcoastal display device using the anti-glare film 1 according to a thirdembodiment. The liquid crystal display device includes, as shown in FIG.8, a liquid crystal panel 31, and a light source 33 provided under theliquid crystal panel 31, and the liquid crystal panel 31 has theanti-glare film 1 on the display side thereof.

The light source 33 supplies light to the liquid crystal panel 31, andhas, e.g., a fluorescent lamp (FL), electroluminescence (EL), or a lightemitting diode (LED). The liquid crystal panel 31 spatially modulatesthe light supplied by the light source 33 to display information. Onboth surfaces of the liquid crystal panel 31 are provided polarizersheets 32 a, 32 b. The polarizer sheet 32 a and polarizer sheet 32 bpermit one of the polarized light components perpendicular to each otherwith respect to the incident light to pass through the sheets and shutout another by absorption. The polarizer sheet 32 a and polarizer sheet32 b are arranged so that, for example, their transmission axes areperpendicular to each other.

The anti-glare film 1 according to a third embodiment has specificdiffuse reflection characteristics as described above, and hence hassuppressed appearance of white muddiness while achieving anti-glareproperties. Further, the anti-glare film has a specific space betweenthe diffuser elements formed in the surface of the anti-glare layer 12,and hence has reduced rough surface appearance. Therefore, by using theanti-glare film 1 in a liquid crystal display devices an image displayedon the liquid crystal display device can be improved in visibility.

EXAMPLES

Hereinbelow, embodiments will be described in more detail with referenceto the following Examples, which should not be construed as limiting thescope of the present application. Examples 1 to 7 and 9 correspond to asecond embodiment of the present application, and Example 8 correspondsto a third embodiment of the present application.

Example 1

Raw materials having the formulation for coating composition show belowwere mixed together and stirred by means of a magnetic stirrer for onehour, and then the resultant coating composition was applied to onesurface of a triacetylcellulose (TAC) film having a thickness of 80 μm(manufactured and sold by Fuji Photo Film Co. Ltd.) by means of a barcoater.

(Formulation of coating composition) Polyfunctional monomer 100 Parts byweight Polymer  5 Parts by weight Photopolymerization initiator(IRGACURE 184,  3 Parts by weight manufactured and sold by CIBA-GEIGY)Solvent (t-butanol) 153 Parts by weight Crosslinkable styrene beads SBX6(manufactured  10 Parts by weight and sold by SEKISUI PLASTICS CO.,LTD.)

After applying, the coating composition applied was dried in a dryingoven at 80° C. for two minutes and then subjected to curing treatment byirradiation with ultraviolet light at 100 mJ/cm2 to obtain an anti-glarefilm in Example 1 in which the dried thickness of the anti-glare layerwas 11.8 μm.

Example 2

An anti-glare film in Example 2 was obtained in substantially the samemanner as in Example 1 except that the amount of crosslinkable styrenebeads SBX6 (manufactured and sold by SEKISUI PLASTICS CO., LTD.) waschanged to 3 parts by weight, and that the dried thickness of theanti-glare layer as 11.0 μm.

Example 3

An anti-glare film in Example 3 was obtained in substantially the samemanner as in Example 1 except that the amount of crosslinkable styrenebeads SBX6 (manufactured and sold by SEKISUI PLASTICS CO., LTD.) waschanged to 5 parts by weight, that the amount of the solvent (t-butanol)was changed to 156 parts by weight, and that the dried thickness of theanti-glare layer was 9.4 μm.

Example 4

An anti-glare film in Example 4 was obtained in substantially the samemanner as in Example 1 except that, instead of crosslinkable styrenebeads SBX6 (manufactured and sold by SEKISUI PLASTICS CO., LTD.), 3parts by weight of crosslinkable styrene beads SBX4 (manufactured andsold by SEKISUI PLASTICS CO., LTD.) were used, and that the driedthickness of the anti-glare layer was 4.7 μm.

Example 5

An anti-glare film in Example 5 was obtained in substantially the samemanner as in Example 1 except that, instead of crosslinkable styrenebeads SBX6 (manufactured and sold by SEKISUI PLASTICS CO., LTD.), 5parts by weight of crosslinkable styrene beads SX500 (manufactured andsold by Soken Chemical & Engineering Co., Ltd.) were used, that theamount of the solvent (t-butanol) was changed to 156 parts by weight,and that the dried thickness of the anti-glare layer was 9.7 μm.

Example 6

In Example 1, 10 parts by weight of crosslinkable styrene beads SBX6(manufactured and sold by SEKISUI PLASTICS CO., LTD.) and 163 parts byweight of a solvent (t-butanol) were mixed together, obtaining ananti-glare film in which the dried thickness of the anti-glare layer was12.3 μm. Then, to the resultant anti-glare film was applied a coatingcomposition prepared by mixing together raw materials having theformulation for coating composition shown below, obtaining an anti-glarefilm in Example 6 having two layers.

(Formulation of coating composition) Polyfunctional monomer 100 Parts byweight Polymer  5 Parts by weight Photopolymerization initiator(IRGACURE 184,  3 Parts by weight manufactured and sold by CIBA-GEIGY)Solvent (t-butanol) 149 Parts by weight

Example 7

An anti-glare film in Example 7 was obtained in substantially the samemanner as in Example 2 except that the coating composition was appliedto one surface of a polyethylene terephthalate (PET) film having athickness of 100 μm (COSMOSHINE A4300 manufactured and sold by TOYOBOCO. LTD.) and that the dried thickness of the anti-glare layer was 10.9μm.

Example 8

A mother die was prepared by a mask imaging method using a KrF excimerlaser and a nickel plating layer was formed on the mother die and thenreleased from the mother die to prepare a first duplicate master. Then,a nickel plating layer as formed on the first duplicate master, and thenreleased from the first duplicate master to prepare a second duplicatemaster. A coating composition having the formulation shown below wasapplied onto the second duplicate master and a polyethyleneterephthalate (PET) film having a thickness of 75 μm (COSMOSHINE A4300,manufactured and sold by TOYOBO CO., LTD.) was put on the coatingcomposition, and a load of 1 kg was applied to the film on the coatingcomposition by means of a rubber roller so that the thickness of thecoating composition became uniform. Subsequently, the polyethyleneterephthalate (PET) film was irradiated with ultraviolet light at 500mJ/cm2 to cure the ultraviolet curing resin, and then the ultravioletcuring resin was released from the second duplicate master to obtain ananti-glare film in Example 8. The dried thickness of the anti-glarelayer was 5.5 μm.

(Formulation of coating composition) Polyfunctional monomer 100 Parts byweight Polymer  5 Parts by weight Photopolymerization initiator(IRGACURE 184,  3 Parts by weight manufactured and sold by CIBA-GEIGY)Solvent (t-butanol) 149 Parts by weight Example 9

An anti-glare film was obtained in substantially the same manner as inExample 1 except that raw materials having the formulation for coatingcomposition shown below were mixed together, and that the driedthickness of the anti-glare layer was 7.3 μm.

(Formulation of coating composition) Polyfunctional acrylic oligomer 100Parts by weight  Photopolymerization initiator (IRGACURE 184,  3 Partsby weight manufactured and sold by CIBA-GEIGY) Solvent (methyl isobutylketone; MIBK) 150 Parts by weight  Propylene glycol monomethyl ether(PGM) 37 Parts by weight Silica beads SS50B (manufactured and sold by 12Parts by weight TOSOH SILICA CORPORATION) Dispersant DOPA15(manufactured and sold by 10 Parts by weight Shin-Etsu Chemical Co.,Ltd.)

Comparative Example 1

An anti-glare film in Comparative Example 1 was obtained insubstantially the same manner as in Example 2 except that the driedthickness of the anti-glare layer was 6.8 μm.

Comparative Example 2

An anti-glare film in Comparative Example 2 was obtained insubstantially the same manner as in Example 2 except that the driedthickness of the anti-glare layer was 7.6 μm.

Comparative Example 3

An anti-glare film in Comparative Example 3 was obtained insubstantially the same manner as in Example 1 except that, instead ofcrosslinkable styrene beads SBX6 (manufactured and sold by SEKISUIPLASTICS CO., LTD.), 3 parts by weight of crosslinkable styrene beadsSX500 (manufactured and sold by Soken Chemical & Engineering Co., Ltd.)were used, and that the dried thickness of the anti-glare layer was 8.5μm.

Comparative Example 4

An anti-glare film in Comparative Example 4 was obtained insubstantially the same manner as in Example 1 except that, instead ofcrosslinkable styrene beads SBX6 (manufactured and sold by SEKISUIPLASTICS CO., LTD.), 5 parts by weight of crosslinkable styrene beadsSX500 (manufactured and sold by Soken Chemical & Engineering Co. Ltd.)were used, and that the dried thickness of the anti-glare layer was 11.2μm.

Comparative Example 5

An anti-glare film in Comparative Example 5 was obtained insubstantially the same manner as in Example 1 except that, instead ofcrosslinkable styrene beads SBX6 (manufactured and sold by SEKISUIPLASTICS CO., LTD.), 5 parts by weight of crosslinkable styrene beadsSBX12 (manufactured and sold by SEKISUI PLASTICS CO., LTD.) were used,and that the dried thickness of the anti-glare layer was 18.7 μm.

With respect to each of the anti-glare films prepared in Examples 1 to 9and Comparative Examples 1 to 5, optical properties were evaluated bythe methods shown below.

Evaluation of Diffuse Reflection Characteristics

For removing the effect of reflection off the back surface to determinediffuse reflection characteristics of the anti-glare film per se, theback surface of each of the anti-glare films prepared in Examples 1 to 9and Comparative Examples 1 to 5 was attached to black glass through anadhesive. The diffuse reflection characteristics were evaluated bydetermining a reflected light intensity under dark room conditions usinga goniophotometer GP-1-3D (manufactured and sold by OPTEC Co., Ltd.) byscanning the collimated incident light upon the sample surface in the−5° direction from −5° to 30° wherein the specular reflection directionwas 0°. In this instance, a luminance meter in the goniophotometer had a2° field of view.

Graphs showing the respective diffuse reflection characteristics inExamples 1 and 2 and Comparative Example 2 are shown in FIG. 9. In FIG.9, L1 corresponds to Example 1, L2 corresponds to Example 2, and L3corresponds to Comparative Example 2. Graphs showing the respectivediffuse reflection characteristics in Examples 3 and 6 and ComparativeExample 4 are shown in FIG. 10. In FIG. 10, L4 corresponds to Example 3,L5 corresponds to Example 6, and L6 corresponds to Comparative Example4. Items of evaluation of the diffuse reflection characteristics are asfollows. An I(α+1)/I(α) ratio was determined wherein I(α) is anintensity of the reflected light at an arbitrary angle α and I(α+1) isan intensity of the reflected light at the angle α by 1° in a wide-angledirection, and a maximum value of the ratio for the reflected lightintensity as determined as maximum change of intensity per 1°. Fullwidths of angle at the ½, 1/100, and 1/1,000 reflected light intensitywith respect to the peak of reflected light intensity were individuallydetermined. A gain was determined by standardizing the reflected lightintensity in the direction at 20° with respect to the specularreflection direction of each of the anti-glare films in Examples 1 to 9and Comparative Examples 1 to 5 using as 1 an intensity of the lightreflected in the specular reflection direction measured using a standarddiffuser plate composed of barium sulfate in the same evaluation.

Measurement of Haze

A haze was measured under the conditions for measurement described inJIS K7136 using a haze meter HM-150 (manufactured and sold by MURAKAMICOLOR RESEARCH LABORATORY). A haze was measured with respect to theanti-glare films in Examples 1 to 9 and Comparative Examples 1 to 5, anda haze was measured with respect to anti-glare films obtained byattaching an adhesive having a haze of 1% or less to the surface of theanti-glare layer of the above anti-glare films. and the latter asdefined as an internal haze, and a difference between the former and thelatter was determined as a surface haze.

Measurement of Average Space Between Diffuser Elements

Regarding each of the anti-glare films in Examples 1 to 9 andComparative Examples 1 to 5, surface roughness was measured under theconditions for measurement described in JIS B0601-1994 using AutomaticMicrofigure Measuring Instrument SURFCORDER ET4000A (manufactured andsold by Kosaka Laboratory Ltd.), and a roughness curve was obtained fromthe resultant two-dimensional cross-sectional curve. As a roughnessparameter, an average length Sm of the trimming curve was determined bymaking a calculation, determining an average space between the diffuserelements.

Evaluation of Anti-Glare Properties

Regarding each of the anti-glare films prepared in Examples 1 to 9 andComparative Examples 1 to 5, for removing the effect of reflection offthe back surface to evaluate anti-glare properties of the anti-glarefilm per se, the back surface of the anti-glare film was attached toblack glass through an adhesive. Then, a fluorescent lighting having twounshaded fluorescent lamps disposed in parallel was used as a lightsource, and a reflection in each anti-glare film was checked by visualobservation from the specular reflection direction, and the reflectionof the fluorescent lighting was evaluated in accordance with thefollowing criteria.

A: Edges of the fluorescent lamps cannot be seen. (The two fluorescentlamps are seen as single light.)

B: The fluorescent lamps can be seen to some extent, but the edges arenot distinct.

C: The fluorescent lamps are directly reflected.

Evaluation of the Degree of White Muddiness

The appearance of white muddiness is perceived by detecting diffusedlight as a light source, such as a fluorescent lighting, which has beendiffused by and reflected off the surface of an anti-glare layer.Therefore, a value quantitatively determined by simulating the abovephenomenon using a commercially available spectrocolorimeter was used asa degree of white muddiness. A specific method for measuring the degreeof white muddiness is as follows. First, with respect to each of theanti-glare films prepared in Examples 1 to 9 and Comparative Examples 1to 5, for removing the effect of reflection off the back surface toevaluate diffuse reflection of the anti-glare film per se, the backsurface was attached to black glass through an adhesive. Then, using anintegrating sphere type spectrocolorimeter SP64 (manufactured and soldby X-Rite, Incorporated), a d/8° optical system was employed in whichthe surface of each anti-glare film was irradiated with diffused lightand the reflected light as measured by a detector positioned in thedirection at 8° with the normal to the anti-glare film. With respect tothe measured value, an SPEX mode in which only the diffuse reflectioncomponent was detected, excluding the specular reflection component, asemployed, and the measurement was conducted at a detection view angle of2°. Experiments have confirmed that there is a correlation between adegree of white muddiness measured by the above method and the degree ofwhite muddiness visually sensed.

With respect to each of the anti-glare films prepared in Examples 1 to 9and Comparative Examples 1 to 5, the back surface was attached to ablack acrylic sheet (ACRYLITE L 502, manufactured and sold by MitsubishiRayon Co., Ltd.) through an adhesive, and a degree of white muddiness inthe resultant anti-glare film was measured in the same manner as in themethod for measurement using black glass. A degree of white muddinessmeasured for the black acrylic sheet having no anti-glare film attachedwas 0.2.

A correlation between the degree of white muddiness measured for theanti-glare film having black glass attached and the degree of whitemuddiness measured for the anti-glare film having a black acrylic sheetattached is described with reference to Table 1 and FIG. 11.

TABLE 1 Degree of white Degree of white Degree of white muddinessmuddiness muddiness (measured) for (measured) for (calculated) for glasssheet acrylic sheet acrylic sheet Sample 1 2.6 2.3 2.3 Sample 2 2.0 1.81.7 Sample 3 0.9 0.5 0.5 Sample 4 0.9 0.6 0.5 Sample 5 1.0 0.6 0.6Sample 6 1.0 0.6 0.6 Sample 7 1.7 1.5 1.4 Sample 8 1.2 0.8 0.9 Sample 91.3 0.9 1.0 Sample 10 1.1 0.7 0.7 Sample 11 1.2 0.8 0.8 Sample 12 1.00.6 0.6 Sample 13 1.0 0.6 0.6 Sample 14 0.9 0.4 0.5

With respect to samples 1 to 14 of anti-glare films obtained by changingthe degree of white muddiness by appropriately controlling the thicknessand particle diameter in the same preparation method as in Example 1,the results of measurement of the degree of white muddiness for thesamples having a black glass sheet attached and for the samples having ablack acrylic sheet attached are shown in Table 1. In addition, withrespect to the degree of white muddiness for the samples having anacrylic sheet attached, values determined by making a calculation usinga regression line obtained from the correlation between a black glasssheet and a black acrylic sheet are shown in Table 1. As can be seenfrom Table 1, values near the measured values can be obtained by thecalculation.

A regression line from the correlation between a black glass and a blackacrylic sheet is obtained by, as shown in FIG. 9, plotting a degree ofwhite muddiness for a sample having a black glass bonded on the abscissaand a degree of white muddiness for a sample having a black acrylicsheet bonded on the ordinate. In FIG. 9, when a degree of whitemuddiness for a sample having a glass sheet attached is taken as x and adegree of white muddiness for a sample having an acrylic sheet attachedis taken as y, a regression line represented by the following formula:

y=1.1039x−0.4735

is obtained, and a determining coefficient R2 is 0.9909. From the above,it is found that there is a close correlation between a degree of whitemuddiness as measured using a black glass and a degree of whitemuddiness as measured using a black acrylic sheet.

Evaluation of Rough Surface Appearance

With respect to each of the anti-glare films prepared in Examples 1 to 9and Comparative Examples 1 to 5, for removing the effect of reflectionoff the back surface to evaluate rough surface appearance of theanti-glare film, the back surface of the anti-glare film was attached toblack glass through an adhesive. Then, the anti-glare film as irradiatedwith light in the direction at about 30° with respect to the normal tothe anti-glare film using a light box (manufactured and sold bag HAKUBAPhoto Industry Co., Ltd.) as a plane light source, and a reflection ineach anti-glare film as checked by visual observation from the specularreflection direction, and the rough surface appearance was evaluated inaccordance with the following criteria.

⊚: Rough surface appearance is not visually perceived even at a positionabout 50 centimeters from the anti-glare film.

∘: Rough surface appearance is not visually perceived at a position 1meter from the anti-glare film, but rough surface appearance is visuallyperceived at a position about 50 centimeters from the film.

×: Rough surface appearance is visually perceived at a position 1 meterfrom the anti-glare film.

The results of the evaluation of the optical properties for Examples 1to 9 and Comparative Examples 1 to 5 are shown in Table 2. With respectto the degree of white muddiness, the results of evaluation for theanti-glare films having black glass attached and the results ofevaluation for the anti-glare films having a black acrylic sheet bondedare shown.

TABLE 2 Full Full Full Average width of width of width of Gain at spaceDegree of Maximum angle at angle at angle at 20° from between whitechange of ½ 1/100 1/1,000 specular Internal Surface diffuser Anti-muddiness Rough intensity intensity intensity intensity reflection hazehaze elements glare Glass Acrylic surface per 1° (°) (°) (°) direction(%) (%) (μm) properties sheet sheet apearance Example 1 0.56 4.2 22.240.9 0.018 40.1 4.5 81 B 1.9 1.6 ⊚ Example 2 0.29 2.4 9.8 19.8 0.00415.5 0.2 204 B 1.1 0.7 ⊚ Example 3 0.42 3.0 14.4 29.2 0.007 17.0 3.0 258B 1.6 1.3 ◯ Example 4 0.11 2.0 7.9 17.4 0.011 8.0 2.1 171 B 1.2 0.9 ⊚Example 5 0.22 1.9 7.7 16.7 0.007 20.6 1.8 216 B 1.0 0.6 ⊚ Example 60.13 2.4 6.7 10.4 0.007 37.4 2.8 194 B 0.9 0.5 ⊚ Example 7 0.28 2.4 9.820.0 0.005 14.9 0.5 223 B 1.1 0.7 ◯ Example 8 0.26 2.2 8.2 15.8 0.0020.5 0.7 126 B 1.0 0.6 ⊚ Example 9 0.11 1.8 6.2 13.2 0.011 0.8 0.0 172 B0.9 0.5 ⊚ Comparative 0.75 7.6 36.8 54.0 0.029 13.8 12.9 164 A 3.3 3.2 ⊚Example 1 Comparative 0.67 6.0 28.8 46.0 0.021 13.6 5.7 110 A 2.8 2.6 ⊚Example 2 Comparative 0.07 1.8 5.4 9.0 0.002 14.1 0.2 210 C 0.9 0.5 XExample 3 Comparative 0.08 1.7 5.8 9.7 0.002 23.1 0.3 199 C 0.9 0.5 XExample 4 Comparative 0.24 2.1 8.8 18.4 0.072 20.9 0.1 339 B 1.2 0.9 XExample 5

Attention is drawn to the maximum change of intensity per 1° shown inTable 2. In each of Examples 1 to 9 in which the maximum change ofintensity per 1° is more than 0.1, the edges of the fluorescent lampswere not distinct in the evaluation of anti-glare properties, and henceeach film is rated rank B, and is found to have appropriate anti-glareproperties. By contrast in Comparative Examples 3 and 4 in which themaximum change of intensity per 1° is 0.1 or less, a reflection of thefluorescent lighting was observed in the evaluation of anti-glareproperties, and the films did not have satisfactory anti-glareproperties. From the above results, it has been found that, forachieving anti-glare properties, the maximum change of intensity per 1°is more than 0.1. In Comparative Examples 1 and 2 in which the maximumchange of intensity per 1° is more than 0.1, the films had excellentanti-glare properties, but they had a gain at 20° as high as 0.02 ormore and had a strong appearance of white muddiness. From this, it hasbeen found that the maximum change of intensity per 1° is preferably 0.6or less.

Next attention is drawn to the full width of angle at the 1/100reflected light intensity. In each of Examples 1 to 9 in which the fullwidth of angle is 6.0° or more, each film achieved appropriateanti-glare properties. By contrast, in Comparative Examples 3 and 4 inwhich the full width of angle is less than 6.0°, a reflection of thefluorescent lighting was observed in the evaluation of anti-glareproperties by visual observation, and the films did not havesatisfactory anti-glare properties. In Comparative Examples 1 and 2 inwhich the full width of angle is more than 28.0°, the films hadexcellent anti-glare properties, but they had a gain at 20° of more than0.02 and had strong appearance of white muddiness. From the aboveresults, it has been found that, for achieving anti-glare properties,the full width of angle at the 1/100 reflected light intensity must be6.0° to 28.0°.

Attention is then drawn to the full width of angle at the 1/1,000reflected light intensity. In each of Examples 1 to 9 in which the fullwidth of angle is 10.0° or more, each film achieved appropriateanti-glare properties. By contrast, in Comparative Examples 3 and 4 inwhich the full width of angle is less than 10.0°, a reflection of thefluorescent lighting was observed in the evaluation of anti-glareproperties by visual observation, and the films did not havesatisfactory anti-glare properties. In Comparative Examples 1 and 2 inwhich the full width of angle is more than 45.0°, the films hadexcellent anti-glare properties, but they had a gain at 20° of more than0.02 and had strong appearance of white muddiness. From the aboveresults, it has been found that, for achieving anti-glare properties,the full width of angle at the 1/1,000 reflected light intensity is be10.0° to 45.0°.

Attention is drawn to the full width of angle at the ½ reflected lightintensity (half band width). Only Comparative Example 1 satisfies therequirement described in Japanese Unexamined Patent Applicationpublication No. 2002-365410 that the half band width with respect to thepeak of reflected light intensity be 7° or more, and the film achievedexcellent anti-glare properties, but the film having a black acrylicsheet attached had a degree of white muddiness of higher than 1.7. Fromthis, it has been found that it is difficult to achieve both excellentanti-glare properties and reduced decree of white muddiness. Further,from a comparison of Comparative Examples 3 and 4 in which theanti-glare properties are unsatisfactory with Example 5 in whichappropriate anti-glare properties are achieved, no relationship in thehalf band width between them is found. From the above, it has been foundthat a film only having a specific full width of angle at the ½reflected light intensity cannot achieve anti-glare properties. Thereason for this is presumed that there is a correlation between thevisibility of a human and a logarithm of the intensity of light andhence the intensity of light must be gradually reduced to the 1/100 or1/1,000 intensity.

The anti-glare films in Examples 1 to 9 having a gain at 20° of 0.02 orless and each having a black acrylic sheet bonded had a degree of whitemuddiness of 1.7 or less in respect of the degree of white muddinessevaluated by, the d/8° reflectance excluding the specular reflectioncomponent. The anti-glare films in Examples 1 to 9 each having a blackacrylic sheet attached had a degree of white muddiness of 1.7 or less,and had reduced black reflection, and therefore, when the films wereactually used in the surface of a display, black was seen sharply.Further, the anti-glare films in Examples 2 and 4 to 9 each having ablack acrylic sheet bonded had a degree of white muddiness of 1.2 orless, and had further reduced black reflection and were improved incontrast, imparting reality to the image. By contrast, the anti-glarefilms in Comparative Examples 1 and 2 having a gain at 20° of 0.02 ormore had strong appearance of white muddiness.

In Comparative Examples 1 and 2 in which the appearance of whitemuddiness is strong, the surface haze is more than 5.0%. From this, itis found that the surface haze is preferably 0 to 5.0%. In each ofExamples 2 to 9, the surface haze is 3.0% or less. From this, it isfound that the surface haze is more preferably 0 to 3.0%. On the otherhand, the internal haze is not particularly specified, and is determinedby adding fine particles required for obtaining a surface shape whichcan achieve desired diffuse reflection characteristics.

Next, attention is drawn to the average space between the diffuserelements. Regarding each of the anti-glare films in Examples 1 to 9having an average space of 300 μm or less, rough surface appearance wasnot perceived in a reflection at a position 1 meter (m) from theanti-glare film. Particularly, each of the anti-glare films in Examples1, 2, 4 to 6, 8, and 9 having an average space of 220 μm or less hadvery fine surface characteristics such that rough surface appearance wasnot perceived even at a position about 50 centimeters(cm) from theanti-glare film. By contrast, regarding the anti-glare film inComparative Example 5 having an average space of more than 330 μm, roughsurface appearance was perceived, and the anti-glare film had no finesurface. Further, regarding the anti-glare films in Comparative Examples3 and 4, each of which has an average space of 300 μm or less, but whichdoes not satisfy, the requirement for the diffuse reflectioncharacteristics that the maximum change of intensity per 1° be more than0.1 to 0.6, the full width of angle at the 1/100 reflected lightintensity be 6.0 to 28.0°, or the full width of angle at the 1/1,000reflected light intensity be 10.0° to 45.0°, serious rough surfaceappearance was perceived. The reason for this is presumed that someuneven portions are caused in a relatively even surface.

The rough surface appearance is easily perceived when the surfaces ofthe fine particles contained markedly protrude from the anti-glare layercomposed of an ultraviolet-curable resin. Therefore, the rough surfaceappearance was further suppressed by covering the surfaces of theparticles with an ionizing radiation-curable resin or the like to reducethe steep slope portions of the particles. In addition, for the samepurpose, classification of the particles to be added to removelarge-diameter particles was also effective.

The anti-glare films in Examples 1 to 9 and Comparative Examples 1 and 5were individually applied to an image display device to check imagelight. In the anti-glare film in Comparative Example 5, markedscintillation called surface glare was observed, whereas, in each of theanti-glare films in Examples 1 to 9, almost no scintillation wasobserved.

From the above results, it is found out that an anti-glare film having,as diffuse reflection characteristics, a specific ratio of the intensityof the reflected light at an arbitrary angle of 10° or less from thespecular reflection direction to the intensity of the reflected lightdeviated from the arbitrary angle by 1° in a wide-angle direction and aspecific gain of the light reflected in the direction at 20° or morefrom the specular reflection direction has suppressed appearance ofwhite muddiness while achieving anti-glare properties. Similarly, it isfounded out that an anti-glare film having a specific full width ofangle at the 1/100 or 1/1,000 reflected light intensity with respect tothe peak of reflected light intensity and a specific gain of the lightreflected in the direction at 20° or more from the specular reflectiondirection has lowered the appearance of white muddiness while achievinganti-glare properties. Further, it is found out that an anti-glare filmhaving a specific average space between the diffuser elements inaddition to the above-mentioned diffuse reflection characteristics hasreduced rough surface appearance.

In a second embodiment of the present application, an example isdescribed in which fine irregularities is formed in the surface due toconvection caused in the resin containing fine particles, but a resincontaining no fine particles can be used as long as Benard Cells areformed in the resin due to convection.

In a third embodiment of the present application, an example isdescribed in which the anti-glare film is used in a liquid crystaldisplay, but the display device is not limited to a liquid crystaldisplay, and the anti-glare film may be applied to various displaydevices, such as a plasma display, an electroluminescence display, and acathode ray tube (CRT) display.

In first and third embodiments of the present application, an example isdescribed in which fine irregularities is formed in the surface of theanti-glare film by a shape transfer method, but an irregularities may beformed in the surface by, for example, subjecting the surface of asubstrate to treatment by a sandblasting method, a laser beam machiningmethod, a wet etching method, or the like.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. An anti-glare film, comprising: a plurality of diffuser elementsformed on a surface; and wherein the anti-glare film has the followingoptical properties as follows: an I(α+1)/I(α) ratio of more than 0.1 to0.6, wherein I(α) is an intensity of a reflected light reflected towardan arbitrary angle α of 10° or less from a specular reflection directionof an incident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface, and I(α+1) is an intensity of a reflected light deviatedfrom the arbitrary angle α by 1° in a wide-angle direction, and a gainof 0.02 or less of a light reflected in the direction at 20° or morefrom the specular reflection direction of the incident light the gainbeing obtained by normalizing a reflected light intensity using aspeculan reflection intensity of a standard diffuse plate as 1, andwherein the diffuser elements have an average space therebetween of 50to 300 micrometers.
 2. The anti-glare film according to claim 1,wherein: the surface has fine irregularities, and the optical propertiesare defined mainly by the fine irregularities.
 3. The anti-glare filmaccording to claim 1, wherein the plurality of diffuser elements areprovided on a substrate to form an anti-glare layer.
 4. The anti-glarefilm according to claim 2, wherein the anti-glare layer is composed of aresin having dispersed therein fine particles having an average particlediameter ranging from 5 nanometers (nm) to 15 micrometers (μm).
 5. Theanti-glare film according to claim 4, wherein the fine particles areagglomerated in the in-plane direction so that the fine irregularitiesare formed in the surface.
 6. The anti-glare film according to claim 5,wherein the agglomerated fine particles are covered with the resin toform the diffuser elements.
 7. The anti-glare film according to claim 6,wherein the resin includes at least one of an ionizing radiation-curableresin and a thermosetting resin.
 8. The anti-glare film according toclaim 6, wherein a surface of the agglomerated fine particles is notexposed, or only a part of the surface of the fine particles positionedat a tip of the diffuser elements is exposed.
 9. The anti-glare filmaccording to claim 6, wherein the diffuser elements have meniscusesformed therebetween.
 10. The anti-glare film according to claim 1, whichhas a surface haze of 5.0 percent (%) or less.
 11. An anti-glare film,comprising: a plurality of diffuser elements formed on a surface; andwherein the anti-glare film has optical properties as follows: a fullwidth of angle of 6.0° to 28.0° at the 1/100 reflected light intensityto a peak of a reflected light intensity, with respect to an incidentlight upon the surface having the plurality of diffuser elements thereonat an angle of 5° to 30° from the normal direction of the surface; and again of 0.02 or less of light reflected in the direction at 20° or morefrom the specular reflection direction of the incident light, the gainbeing obtained by normalizing a reflected light intensity using aspecular reflection intensity of a standard diffuse plate as 1, whereinthe diffuser elements have au average space therebetween of 50 to 300micrometers.
 12. An anti-glare film comprising: a plurality of diffuserelements formed on a surface; and wherein the anti-glare film hasoptical properties as follows: a full width of angle of 10.0° to 45.0°at the 1/1000 reflected light intensity to a peak of a reflected lightintensity, with respect to an incident light upon the surface having theplurality of diffuser elements thereon at an angle of 5° to 30° from thenormal direction of the surface, and a gain of 0.02 or less of a lightreflected in the direction at 20° or more from the specular reflectiondirection of the incident light, the gain being obtained by normalizinga reflected light intensity using a specular reflection intensity of astandard diffuse plate as 1 and wherein the diffuser elements have anaverage space therebetween of 50 to 300 micrometers.
 13. A method formanufacturing an anti-glare film, the method comprising: forming fineirregularities in a surface of the anti-glare film by shape transfermethod, sandblasting method, laser beam machining method wet etchingmethod or Benard Cells forming method, to thereby form a plurality ofdiffuser elements on the surface thereof, wherein the anti-glare filmhas optical properties as follows: an I(α+1)/I(α) ratio of more than 0.1to 0.6, wherein I(α) is an intensity of a reflected light reflectedtoward an arbitrary angle α of 10° or less from a first specularreflection direction of an incident light upon the surface having theplurality of diffuser elements thereon at an angle of 5° to 30° from thenormal direction of the surface, and I(α+1) is an intensity of areflected light deviated from the arbitrary angle α by 1° in awide-angle direction, and a gain of 0.02 or less of a light reflected inthe direction at 20° or more from the specular reflection direction ofthe incident light the gain being obtained by normalizing a reflectedlight intensity using a specular reflection intensity of a standarddiffuse plate as 1, and wherein the diffuser elements have an averagespace therebetween of 50 to 300 micrometers.
 14. The method according toclaim 13 wherein the fine irregularities forming step using the shapetransfer method comprises: feeding a resin into a mold; and curing theresin fed into the mold and releasing the cured resin from the mold. 15.The method according to claim 14 wherein the fine irregularities formingstep further comprises before the resin feeding into the mold step,forming the fine irregularities in the mold by a sandblasting, wetetching, or laser beam machining method.
 16. The method according toclaim 13, wherein the fine irregularities forming step using BenardCells forming method comprises: applying a coating composition includingfine particles, a resin, and a solvent to a substrate; drying theapplied coating composition to cause convection in the coatingcomposition so that the fine particles are agglomerated by theconvection; and curing the dried coating composition.
 17. The methodaccording to claim 16, wherein, in the applied coating compositiondrying step, Benard Cells are formed by the convection.
 18. A method formanufacturing an anti-glare film, the method comprising: forming fineirregularities in a surface of the anti-glare film by shape transfermethod, sandblasting method, laser beam machining method, wet etchingmethod, or Benard Cells forming method, to thereby form a plurality ofdiffuser elements on the surface thereof, and wherein the anti-glarefilm has optical properties as follows: a full width of angle of 6.0° to28.0° at the 1/100 reflected light intensity to a peak of a reflectedlight intensity, with respect to an incident light upon the surfacehaving the plurality of diffuser elements thereon at an angle of 5° to30° from the normal direction of the surface; and a gain of 0.02 or lessof a light reflected in the direction at 20° or more from a specularreflection direction of the incident light, the gain being obtained bynormalizing a reflected light intensity using a specular refectionintensity of a standard diffuse plate as 1, and wherein the diffuserelements have an average space therebetween of 50 to 300 micrometers.19. A method for manufacturing an anti-glare film, the methodcomprising: forming fine irregularities in a surface of the anti-glarefilm by shape transfer method, sandblasting method, laser beam machiningmethod, wet etching method, or Benard Cells forming method, to therebyform a plurality of diffuser elements on the surface thereof, andwherein the anti-glare film has optical properties as follows: a fullwidth of angle of 10.0° to 45.0° at the 1/1,000 reflected lightintensity to a peak of a reflected light intensity, with respect to anincident light upon the surface having the plurality of diffuserelements thereon at an angle of 5° to 30° from the normal direction ofthe surface, and a gain of 0.02 or less of a light reflected in thedirection at 20° or more from a specular reflection direction of theincident light, the gain being obtained by normalizing a reflected lightintensity using a specular reflection intensity of a standard diffuseplate as 1, and wherein the diffuser elements have an average spacetherebetween of 50 to 300 micrometers.
 20. A display device comprising:a display portion for displaying an image; and an anti-glare film formedon a display side of the displays portion, wherein the anti-glare filmhaving a plurality of diffuser elements on a surface of the anti-glarefilm, and having optical properties as follows: an I(α+1)/I(α) ratio ofmore than 0.1 to 0.6, wherein I(α) is an intensity of a reflected lightreflected toward an arbitrary angle α of 10° or less from a specularreflection direction to an incident light upon the surface having theplurality of diffuser elements thereon at an angle of 5° to 30° from thenormal direction of the surface, and I(α+1) is an intensity of areflected light deviated from the arbitrary angle α by 1° in awide-angle-direction, and a gain of 0.02 or less of a light reflected inthe direction at 20° or more from a specular reflection direction of theincident light, the gain being obtained by normalizing a reflected lightintensity using a specular reflection intensity of a standard diffuseplate as 1, and wherein the diffuser elements have an average spacetherebetween of 50 to 300 micrometers.
 21. A display device comprising:a display portion for displaying an image; and an anti-glare film formedon a display side of the display portion, wherein the anti-glare filmhaving a plurality of diffuser elements on a surface of the anti-glarefilm, and having the optical properties as follows: a full width ofangle of 6.0° to 28.0° at the 1/100 reflected light intensity to a peakof a reflected light intensity, with respect to an incident light uponthe surface having the plurality of diffuser elements thereon at anangle of 5° to 30° from the normal direction of the surface; and a gainof 0.02 or less of a light reflected in the direction a 20° or more froma specular reflection direction of the incident light, the gain beingobtained by normalizing a reflected light intensity using a specularreflection intensity of a standard diffuse plate as 1, and wherein thediffuser elements have an average space therebetween of 50 to 300micrometers.
 22. A display device comprising: a display portion fordisplaying an image; and an anti-glare film formed on a display side ofthe display portion, wherein the anti-glare film having a plurality ofdiffuser elements on a surface of the anti-glare film, and havingoptical properties as follows: a full width of angle of 10.0° to 45.0°at the 1/1,000 reflected light intensity to a peak of a reflected lightintensity with respect to an incident light upon the surface having theplurality of diffuser elements thereon at in angle of 5° to 30° from thenormal direction of the surface, and a gain of 0.02 or less of a lightreflected in the direction at 20° or more from a specular reflectiondirection of the incident light, the gain being obtained by normalizinga reflected light intensity using a specular reflection intensity of astandard diffuse plate as 1, and wherein the diffuser elements have anaverage space therebetween of 50 to 300 micrometers.